The IEEE 802.16 specifies a fixed Broadband Wireless Access (BWA) standard for a wireless Metropolitan Area Network (MAN). The IEEE 802.16 standard defines different physical layer technologies for different frequency bands, and is mainly applied to residential, Small Office/Home Office (SOHO), remote operators, and Small-Medium Enterprise (SME) markets.
In an IEEE 802.16 system, a Media Access Control (MAC) layer is able to support tough user environments, cope with an application environment that each channel may have hundreds of users, and support continuous and burst traffics. The IEEE 802.16 system has an Asynchronous Transfer Mode (ATM) Convergence Sublayer (CS) and a packet CS, provides encapsulation of multiple data units from an upper layer into one MAC Protocol Data Unit (PDU) for transmission, thereby realizing transparent processes of ATM, IP and Ethernet services.
It can be seen from the above descriptions that, the IEEE 802.16 system may have wide applications.
In current communication systems, multicast and broadcast are employed for transmitting data from one source to multiple destinations. In traditional mobile networks, a Cell Broadcast Service (CBS) allows transmission of low bit-rate data to all users through a common broadcast channel of a cell. The CBS service belongs to a message service.
In order to effectively utilize radio resources, the latest edition of the IEEE 802.16, i.e., IEEE 802.16e/D5, has introduced the MBS service which standardizes the Point to Multi-point transmission in the mobile network, thereby implementing network resources sharing and raising the utilizing rate of the network resources especially air interface. The newly-introduced MBS service may implement not only the multicast and broadcast of low bit-rate message services such as text, but also the multicast and broadcast of high bit-rate multimedia services, which is in the trend of development of future mobile data transmission.
A Mobile Service Station (MSS) receives the MBS service through an MBS_MAP message. Information Elements (IEs) of the MBS_MAP message are as shown in Table 1.
TABLE 1SyntaxSizeNotesMBS-MAP_Message_Format( ) {Management Message Type =8 bitsFrame number24 bits The frame number is identical to theframe number in the DL-MAPfor (i = 0; i < n; i++) {Multicast CID12 bits 12 LSB of CID for multicastMBS DIUC4 bitsOFDMA Symbol offset8 bitsOFDMA symbol offset with respect tostart of the MBS zoneSubchannel offset6 bitsBoosting3 bits000: normal (not boosted); +6 dB;010: −6 dB; 011: +9 dB; 100: +3 dB;101: −3 dB; 110: −9 dB; 111: −12 dB;No. OFDMA Symbols7 bitsNo. Subchannels6 bitsRepetition Coding Indication2 bits0b00 -No repetition coding0b01 -Repetition coding of 2 used0b10 - Repetition coding of 4 used0b11 -Repetition coding of 6 usedNext MBS frame offset8 bitsThe Next MBS frame offset value islower 8 bits of the frame number inwhich the BS shall transmit the nextMBS frame.Next MBS OFDMA Symbol8 bitsThe offset of the OFDMA symbol inoffsetwhich the next MBS zone starts,measured in OFDMA symbols from thebeginning of the downlink frame inwhich the MBS-MAP is transmitted.}if !(byte boundary) {Padding Nibble4 bitsPadding to reach byte boundary}}
It can be seen from Table 1 that, the MBS_MAP message provides physical channel resources allocated for a specific Multicast CID, i.e. an MBS service, in a given MBS ZONE. The physical channel resources include occupied OFDM symbols and used Subchannels. The MBS_MAP message also provides Downlink Interval Usage Code (DIUC) and Boosting for a given burst, and the Next MBS frame offset and the Next MBS OFDMA Symbol offset for determining the location of the next MBS frame.
Based on the above MBS_MAP message, when receiving the first MBS frame, the MSS needs to locate the MBS_MAP message according to an MBS_MAP Information Element (MBS_MAP_IE) in a DL_MAP message, and determines the physical channel resources occupied by the MBS_MAP message, the DIUC of the MBS_MAP message, and may also determine the start transmission point of the MBS Zone at the same time. And then the MSS determines the physical channel resources occupied by the first MBS frame and the DIUC of the first MBS frame according to MBS data resources and DIUC assigned by the MBS_MAP message, thereby receiving the first MBS frame in the MBS Zone. At the same time, the MSS may determine the location of the next MBS frame according to the Next MBS frame offset and the Next MBS OFDMA Symbol offset in the current MBS_MAP message. Thus, there is no need to receive the DL_MAP message to determine the location of the next MBS frame.
Although the location of the next MBS frame may be determined according to the current MBS_MAP message, the applicant finds out that the physical channel resources occupied by the next MBS frame and the DIUC of the next MBS frame further need to be determined to receive the next MBS frame. Therefore, it is necessary to acquire the MBS_MAP message associated with the next MBS frame before the arrival of the next MBS frame, so as to determine the physical channel resources occupied by the next MBS frame and the DIUC of the next MBS frame from the MBS-MAP message.
However in the MBS-MAP message defined by the current IEEE 802.16 standard, only the Next MBS frame offset and the Next MBS OFDMA Symbol offset are related with the next MBS frame. Although the location of the next MBS_MAP message may be determined according to the Next MBS OFDMA Symbol offset in the current MBS-MAP message, the physical channel resources occupied by the next MBS_MAP message and the DIUC of the next MBS_MAP message cannot be determined. Therefore, when the next MBS frame comes, the MSS cannot determine the physical channel resources occupied by the MBS_MAP message corresponding to the next MBS frame and the DIUC of the MBS_MAP message corresponding to the next MBS frame according to the current MBS_MAP message. Since the MSS cannot locate the next MBS_MAP message accurately, the physical channel resources occupied by the next MBS frame and the DIUC of the next MBS frame cannot be obtained from the MBS_MAP message.
To sum up, the applicant finds out that in the technical scheme taught by the current solution, the MSS cannot determine the physical channel resources occupied by the next MBS_MAP message and the DIUC of the next MBS_MAP message according to the current MBS_MAP message, therefore, the MSS cannot receive the MBS service directly.